1. Field of the Invention
The present invention relates generally to by-pass valves to provide for by-pass of fluid within a well casing past a well tool having packer elements as the tool is being run into a well to provide a well servicing activity. More particularly, the present invention concerns a by-pass valve having a unique closable sleeve valve that provides an alternative flow path for displaced well fluids to travel across flow sensitive or restrictive bottom hole assemblies.
2. Description of the Prior Art
The process of conveying tools into well bores filled with fluid generally involves a displacement of fluids. During conveyance of a well tool within a well, fluids must be transferred from below the tool into the tubing and/or annulus above the tool or vice versa. Bull-heading, i.e., displacing well fluid into a reservoir, is often unacceptable as it can lead to well control problems, cause formation damage and can induce pressure surges that are intolerable by some flow or pressure sensitive devices. In many applications the displaced fluid may be channeled around the tool and/or through the tool into the tubing. However, in some applications the tubing may be intentionally blocked, or the device may utilize cup type or flow sensitive sealing elements which may prevent displaced fluid flow externally of the tool.
Tools used in coiled tubing applications often restrict both the tubing and external flow paths, and may include cup type, pressure and flow sensitive sealing elements. These tools generally include a dedicated internal by-pass, or internal flow path. An internal by-pass through a tool is often defined as a tortuous or restricted flow path or paths which tend to restrict the flow of displaced fluid. To contend with such restrictions well service tools are often run in or moved at a slow controlled rate. Tools using cup type self energizing sealing elements are very sensitive to differential pressure or flow and may become prematurely energized if the tool run in speed exceeds the by-pass capabilities.
Mechanical by-pass valves, also referred to as unloader valves, which are normally actuated by axial motion, or a combination of axial and rotational motion, controlled from the surface have been used to allow self filling of the tubing and dedicated circulation paths, have been used in jointed pipe operations. Similar mechanical devices may have been used with coiled tubing, however, the inventors are not aware of the existence of any automatic, hydraulic type actuated valve used with coiled tubing for the purpose of relieving pressure sensitive devices or formations. Electronic/hydraulic, pressure operated valves such as the IRIS™ have also been used for similar jointed pipe applications; however, they are very complicated, expensive and, due to their relatively large OD (greater than 4″) and long length, it is unlikely that such a valve could be feasibly applied to coiled tubing applications.